1 / 23

Polymethyl Methacrylate

Polymethyl Methacrylate. (PMMA). Monomer. Methyl Methacrylate (MMA) Formula : H 2 C = CHCOOCH 3 Structure :. Formation. Free Radical Polymerization. Step 1 : Free radical (R*) plus methyl methacrylate. →.

ethan-strickland
Télécharger la présentation

Polymethyl Methacrylate

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Polymethyl Methacrylate (PMMA)

  2. Monomer • Methyl Methacrylate (MMA) Formula : H2C = CHCOOCH3 Structure :

  3. Formation • Free Radical Polymerization

  4. Step 1 : Free radical (R*) plus methyl methacrylate →

  5. Step 2 : Polymerization - MMA radical plus MMA :repeated many, many times Step 3 : Termination – occurs when two radicals join

  6. Catalysts • Multiple catalysts can be used in production of PMMA. Some of these are: • Butyl Lithium • Highly active catalysts based on group 4 metallocenes • An aluminum system supported by salen ligands

  7. Why Use Different Catalysts? • Different catalysts result in different versions of the polymer • Variation is due to the placement of the ester (R-O-R) and methyl (CH3) groups along the polymer backbone

  8. Isotactic – similar groups on same side of chain • Syndiotactic – two groups alternate • Atatactic – displays no regular pattern • Every other carbon in the chain is a steriocenter

  9. History of PMMA • Developed by three companies at approximately the same time in 1928 • Röhm and Haas • Du Pont • ICI (Imperial Chemical Industries) • First came on market 1933

  10. Historical uses of PMMA • Du Pont first used PMMA primarily for cast products (rods, tubes, and blocks) • ICI and Röhm and Haas focused on producing sheets of PMMA to be used as safety glass • Röhm and Haas introduced Plexiglass to market in 1936 and ICI followed with Perspex later that same year

  11. Properties of PMMA • Lighter than glass (density is about half that of glass) • Shatter proof • Softer and easier to scratch than glass (scratch resistant coatings may be applied) • Transmits more light than glass (92% of visible light) • Does not filter UV light (may be coated with UV film) • More transparent than glass, so windows can be made thicker

  12. Current uses for PMMA • Include many uses similar to those for which it was first developed but include many things never imagined by the inventors! A partial list of the uses for PMMA includes:

  13. Safety glass such as Plexiglass and Lucite – uses range from windows for aquariums and under-water restaurants to safety shields at hockey rinks to skylights in your home to simple paperweights

  14. Medical Uses • Used as bone cement for use in arthroplastic procedures of the hip, knee, and other joints for the fixation of polymer or metallic prosthetic implants to living bone • Used in Pacemakers

  15. Dentures!

  16. Artificial eye lenses used for cataract surgery • Suspended in collagen and implanted to reduce wrinkles in cosmetic procedures

  17. Acrylic Paints • Acrylic “latex paints” often contain PMMA suspended in water

  18. Blacklight Tattoo Ink • Made of 97.5% PMMA and 2.5% microspheres of fluorescent dye suspended in UV sterilized, distilled water with no preservatives or other additives • The ink received USFDA approval in 1995 for use in animals, plants and fish for the purpose of tracking migration, growth patterns; breeding habits etc.

  19. Breakdown of PMMA • Autoignites at 445° C (833° F) • Burns cleanly to produce H2O and CO2 • Virtually smokeless combustion • Has superior recyclability • Can be reground and reused • Can be depolymerized back to monomer, purged of impurities, and reploymerized back to PMMA

  20. Potential Toxicity • PMMA is an essentially non-toxic material • No workplace exposure limits • MMA • Respiratory effects may result from chronic low level exposure or from short term acute exposure • Exposure primarily occupational (production of monomer and its polymers, doctors, nurses, dentists, and dental technicians)

  21. Ingestion of PMMA/MMA • Oral LD50 (in rats) PMMA = 11,700 mg/kg • Oral LD50 (in rats) MMA – 7,872 mg/kg

More Related